It is well known, in the railroad industry, that railway cars can be connected together by different types of coupler members. Such couplers may be conventional couplers, articulated couplers or drawbars. Conventional couplers are independent units disposed on an end of each car which interconnect with one another, between the ends of adjacent cars, to form a connection. Conventional couplers are used on cars which generally require frequent disconnections. On the other hand, drawbar assemblies are integral units which extend between the ends of two adjacent cars to form a generally semipermanent connection therebetween. Nevertheless, in either instance, a shank end of the coupler or drawbar will extend into the center sill portion of a railway car where it is secured so as to transmit the longitudinal forces exerted to the car during in track service. Additionally, each type coupler system requires the use of generally common components to enable draft loads to be safely applied to the end of the railway car. For example, yokes, draft stops (front and rear) and draft keys.
In addition, some prior inventions have been directed to improvements in the center sill construction for receiving primarily conventional couplers. However, these improvements may also have application in receiving couplers in a slackless drawbar arrangement. By slackless, it is meant that the drawbar (or coupler) is received within the center sill member in a manner to minimize longitudinal play or movements. However, because it is important for successive railway cars in a train to be able to accommodate relative movement between cars when curves and inclines are to be negotiated, there must be provision made for each car to move in pitch, yaw and roll modes with respect to the coupler member. Furthermore, there must be some provision made to periodically remove the worn and/or broken draft components for repair and/or replacement of parts and, in connection with the slackless drawbar systems, to disconnect adjacently connected railway cars.
In a slackless drawbar system, for example, the coupler member is usually held in a way to eliminate, or at least minimize, the longitudinal movement with respect to the railway car body. This is usually accomplished by providing a tapered wedge member between a rear wall of a pocket casting, or yoke, (secured in the center still) and a follower block member which rests against the butt end of the drawbar member. The tapered wedge member tends to force the follower block member away from the pocket casting end wall and firmly against the butt end of the drawbar member shank. When the cars are being pushed, during operation, the longitudinal forces exerted will cause compression of the drawbar member against the follower block member, tapered wedge member and pocket casting end wall.
Conversely, when the railway cars are being pulled, the longitudinal forces being exerted, which tend to separate the drawbar from the pocket casting, are countered in some slackless drawbar systems by a draft key which is a metal bar that extends laterally of the car center sill member through slots provided in the sidewalls of the center sill member and a slot formed in the shank portion of the coupler member and in other slackless drawbar systems through slots which are formed through the front draft stop members.
In such slackless drawbar systems, the drawbar is held tightly between the bearing block member and the follower block member by operation of the tapered wedge member which separates the pocket casting and follower block member and compresses the follower block member against the drawbar to force the latter against the bearing block member and the follower block member. However, the mating surfaces of the follower block member and drawbar are, preferably, curved to permit the drawbar to pivot slightly both a vertically and a lateral direction and to permit the railway car to roll with respect to the drawbar.